Fabrication of novel porous anodic alumina membranes by two-step hard anodization

Abstract

Porous anodic alumina (PAA) membranes with highly ordered hexagonal cells anda novel pore structure have been fabricated by two-step hard anodization in aH2SO4–Al2(SO4)3–H2O system at 40 and 50 V, giving average cell diameters of 77 and 96 nm, respectively. There areseveral tiny pores embedded in each big shallow pore on the top of the membranes, andthere is only one pore in one cell at their bottom. The cells on both sides of the membranespresent almost the same periodic arrangement. In order to explore the formation of thenovel pore structure, PAA membranes fabricated at different current densities(30–200 mA cm−2) are obtained by maintaining a constant voltage at 40 V. The experimental results showthat the interpore distance is not only dependent on the anodization voltage, but is alsoinfluenced by the current density, which means that the pore structure of PAA membranesfabricated by hard anodization can be accurately designed and controlled by adjusting theanodization voltage and current density simultaneously.